Large crowds are expected Friday for the second-to-last launch of the United States' space shuttle program.

Officials are anticipating as many as 750,000 spectators near the Kennedy Space Center in Florida for the afternoon launch of Space Shuttle Endeavour. The crowd will include U.S. President Barack Obama, his wife Michelle and their two daughters.

The mission will be the 25th and final one for Endeavour, which will be decommissioned and put on permanent display at the California Science Center in Los Angeles upon its return to Earth.

During its two weeks in space, Endeavour and its six-man crew will deliver a $2 billion scientific instrument to the International Space Station (ISS). The instrument is designed to search for cosmic rays throughout the universe.

The mission has also attracted attention because of the shuttle's commander. Mark Kelly's wife is U.S. Representative Gabrielle Giffords, who is recovering from a near-fatal shooting in January during a political meeting in her Arizona congressional district. Giffords is expected to watch her husband's launch in a secluded area at the Kennedy Space Center.

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The crew also includes Italy's Roberto Vitorri, who is flying as a member of the European Space Agency.

Endeavour is expected to return to Earth on May 13. NASA's 30-year space shuttle program will end in June after Atlantis' final mission to the ISS.

NASA has started working with four private companies on vehicles to replace the space shuttles. Those vehicles could be ready in 2013, depending on the availability of government funding.

In attending Endeavor's launch Friday, President Obama will become just the second president to attend a shuttle launch. President Bill Clinton was on hand for the 1998 launch of space shuttle Discovery, which carried pioneering astronaut John Glenn back into space 36 years after he became the first American to orbit the Earth.

Endeavour is the sixth vehicle in the U.S. space shuttle fleet, built to replace its sister shuttle Challenger, which exploded shortly after liftoff in January 1986, killing all seven crew members. It was named after the historic British naval vessel that explored the South Pacific in the 18th century. Endeavour's first flight was on May 7, 1992.